Pilot-based parametric channel estimation algorithm for DCO-OFDM-based visual light communications

Abstract

Due to wide modulation bandwidth in optical communication, multipath channels may be non-sparse and deteriorate communication performance heavily. Traditional compressive sensing-based channel estimation algorithm cannot be employed in this kind of situation. In this paper, we propose a practical parametric channel estimation algorithm for orthogonal frequency division multiplexing (OFDM)-based visual light communication (VLC) systems based on modified zero correlation code (ZCC) pair that has the impulse-like correlation property. Simulation results show that the proposed algorithm achieves better performances than existing least squares (LS)-based algorithm in both bit error ration (BER) and frequency response estimation.

Low-Complexity Joint Time Synchronization and Channel Estimation for OFDM-Based PLC Systems

“…the constant amplitude pilot symbols, under the same threshold. In order to clarify this, the same scheme from [28], considering only AWGN, is also shown in Fig. 7, and it is noticed that the performance is very similar to the ones obtained from [19], [26] and the proposed scheme in both channels.…”

“…It is also clear that the MSE is higher for CH II than for CH I. On the other hand, the timing MSEs of the schemes based on the ZCC pair [27], [28] are significantly higher. This occur because the sequence is windowed in the time domain, leading to a high peak to average power ratio (PAPR).…”

“…7, evaluated in terms of the timing MSE under both channels conditions CH I and II. Also, the MSEs of the fine synchronization process considering the schemes based on PN [26], MOS [19] and ZCC pair of sequences [27], [28] are included for comparison. The same thresholding criteria γ sub 2 is used in all cases, in order to have the same probability of detecting the first channel tap.…”

“…The cross correlation of a complex sequence-based pilot symbol as in [19] would demand up to N complex multipliers and N − 1 complex adders. The pilot symbol based on ZCC pair [28], requires 2 • N real multipliers and 2 • N − 2 real adders, and the one based on binary PN sequence requires 2 • N − 2 real adders to perform the cross correlation [26]. Table I shows the number of operations required to compute the cross correlation of the proposed pilot symbol and some previous works in terms of real-valued arithmetic operations, for a length N .…”

“…On the other hand, sequence-based pilot symbols have been proposed for joint time synchronization and channel estimation, where the CIR estimation can be obtained directly from the output of the matched filter used in the fine synchronization stage [19], without the need of the DFT process as in the previous DFT-based channel estimation techniques. Different types of sequences have been proposed for the design of sequence-based pilot symbols, such as pseudo-noise (PN) sequences [12], [26], Zadoff-Chu [17], modulatable orthogonal sequences (MOS) [19], or zero correlation code (ZCC) pairs [27], [28]. As the complexity associated with the computation of the CC is still high in these schemes, the design of low-complexity PLC synchronization and channel estimation becomes attractive.…”